The field of the invention relates generally to a method and an apparatus for micropelletizing a material, and more particularly, to a method and apparatus that utilizes Rayleigh disturbances to form micropellets.
Micropelletization is a relatively new technology that provides a variety of potential applications. Conventional pellets have cross-sectional dimensions (e.g., diameters) of 2.5 mm to 5 mm, while micropellets have cross-sectional dimensions (e.g., diameters) less than 2 mm, such as from 2 mm to about 50 microns, or even smaller.
In one example, the use of micropellets in polymer processing has noted benefits. For example, potential benefits of micropellets include: high surface to volume ratio, high bulk density, fast and even melting rates in extrusion, improved dry flow properties, faster injection molding cycles, and consequently lower energy consumption during processing. Moreover, more specialized sintering processes, such as laser sintering techniques, microporous plastics parts manufacturing, and other powder sintering methods actually depend on micropellets. In these processes, particle shape and size as well as size distribution play a significant role in process control and quality of the finished product. For example, wide ranges in size distribution deliver particles that may be too small when laser sintering, resulting in agglomeration of particles. Also, spherical particle geometries may be preferred with respect to reproducibility and surface quality.
Unfortunately, some of the conventional processes that can be found in the market produce micropellets that may not be uniform in shape and have wide ranges in size and shape distribution. Such conventional micropelletization processes are basically identical to the methods for producing standard pellet sizes. Some commercial processes for producing micropellets are thread and underwater pelletizers, which produce micropellets having cylindrical and spherical shapes, respectively. Both processes utilize cutters with blades. These cutters exert torsional forces that can produce micropellets with irregular shapes and surfaces.